The role of catalytic nanoparticle pretreatment on the growth of vertically aligned carbon nanotubes by hot-filament chemical vapor deposition

•Effect of the atomic hydrogen assisted pre-treatment on the growth of VACNT using hot-filament CVD.•Pre-treatment time and process temperature tune the density, the shape and the structure of the CNTs.•Correlations between size and density of the as-formed catalyst and the CNT’s structure and density.•Carbon nanotubes synthesized at low temperature down to 500 °C using spayed iron chloride salts.•Density of the CNT carpet adjusted by catalytic nanoparticle engineering.

The effect of atomic hydrogen assisted pre-treatment on the growth of vertically aligned carbon nanotubes using hot-filament chemical vapor deposition was investigated. Iron nanoparticle catalysts were formed on an aluminum oxide support layer by spraying of iron chloride salt solutions as catalyst precursor. It is found that pre-treatment time and process temperature tune the density as well as the shape and the structure of the grown carbon nanotubes. An optimum pre-treatment time can be found for the growth of long and well aligned carbon nanotubes, densely packed to each other. To provide insight on this behavior, the iron catalytic nanoparticles formed after the atomic hydrogen assisted pre-treatment were analyzed by atomic force microscopy. The relations between the size and the density of the as-formed catalyst and the as-grown carbon nanotube's structure and density are discussed.